Bacterium E. coli-536 – Unwelcome Guest in the Intestine

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Small holes in the intestinal wall can contribute to inflammatory bowel disease

Scientists at the Charité – Universitätsmedizin Berlin are deciphering a heretofore unknown mechanism in the context of chronic inflammatory bowel disease. The coli bacteria that produce the protein alpha-haemolysin play an important role in inflammatory processes in the intestines. As now discovered by the physicians and biologists at the Institute of Clinical Physiology of the Charité, the toxic substance alpha-haemolysin can cause small holes in the intestinal wall, i.e. channels for inflammation-triggering substances. The results of their study have been published in the scientific journal Gut*.

Most bacterial strains of Escherichia coli are considered to be symbiotic guests in intestinal flora; certain of these possess probiotic, health-promoting characteristics. However, other coli bacteria and in particular those that can cause urinary tract infections – E. coli-536 for example – possess characteristics that can lead to, or exacerbate existing inflammatory bowel disease. Using an animal model and with the help of human cell samples, researchers working together with Prof. Dr. Jörg-Dieter Schulzke have demonstrated that the cell toxin alpha-haemolysin of these coliform bacteria provokes small holes in the intestinal wall. Scientists call these holes "focal leaks". Such focal leaks make it possible for substances to pass from the intestine into the body and thereby provoke inflammation.

"In patients with ulcerative colitis – a commonly occurring, chronic, inflammatory bowel disease – we were able to demonstrate the increased presence of alpha-haemolysin in the intestinal wall. This finding shows that the coli bacteria are indeed a factor in the disease process, over and above any preexisting genetic disposition", says Dr. Roland Bücker, the study's lead author. Bacteria that impair the sealing function of the intestinal mucosa, such as alpha-haemolysin-carrying E. coli, will now assume greater importance in terms of how we deal with inflammatory bowel disease. The present study also provides a basic understanding of how to best develop new therapeutic methods such as bacteriotherapy or dedicated vaccinations.